During the initial development of a community, a series of networked conduits are required to pipe sanitary sewage and storm sewage away from the community to, for example, a processing, treatment, or drainage site. Sanitary sewage and storm sewage systems are typically comprised of a plurality of networked pipelines that are buried in roadways deep enough to minimize the effects of heavy vehicles passing over the roadways and also deep enough (for example, below the frost line) to avoid the negative effects of freezing temperatures. In order to provide access to the pipeline for inspection and maintenance, manholes or catch basins are periodically interconnected within the networked pipelines. The manholes and/or catch basins are buried beneath the earth's surface, and typically below roadways, at depths of 10 feet or more.
When a manhole or catch basin is first constructed, it typically comprises a base, risers, cone, support frame and manhole cover or grate. The base includes a bottom with concentric sidewalls extending upward from the bottom. The lower portion of the base of the manhole is referred to as a canal-bed. The base of the manhole or catch basin structure may include one or more openings adapted to receive the pipeline, wherein the canal-bed includes a channel that directs fluid passing between the interconnected pipelines. One or more hollow cylindrical risers rest atop the base sidewalls, thereby increasing the sidewall of the manhole to a desired height. The cone is hollow and is stacked atop the uppermost riser, wherein one end of the cone is sized to fit on top of the riser and the other end of the cone has a reduced diameter suitable for receiving and supporting the support frame on top of the cone.
The base, risers and cone of the manhole structures are typically comprised of mortared blocks or pre-cast with concrete and may weigh several tons. Of course, the overall size of the base, including the internal and external diameters of the base sidewalls affects both the cost to manufacture the base and the cost to construct the manhole. Thus, it is desirable to decrease the diameter of the base as much as practical. However, oftentimes communities will require that an unobstructed inner diameter of the base, risers, and access opening must be equal or exceed predefined minimums for rigidity, stability and access. Hence, the desire to reduce costs associated with the manhole may be limited by minimum size requirements.
Over time it may be desirable to add or interconnect an additional drainage or sewage line to the main system. In the past, it has been customary to excavate the area around the manhole the entire depth of the manhole and interconnect the expansion pipeline to the main pipeline on the outside of the manhole. This connection of the expansion line to the main line is commonly referred to as an outside drop. Although it would be preferable to pass the expansion line through a portion of the vertical cross section of the manhole (commonly referred to as an inside drop), thereby reducing the added expense associated with a complete excavation, the internal size requirements of the manhole does not typically allow for the added size of the convention pipeline. Hence, there is a need for an inside drop that, when positioned within the manhole, does not to exceed the internal size requirements.
Once the manhole or catch basin is constructed, fluids passing therethrough tend to deteriorate the structure. For example, sewage and putrid water are very acidic, and may comprise hydrogen sulfide and sulfuric acid. Over time, exposure to sewage or putrid water can damage the concrete of the canal-bed, base, and cone. In catch basins, road salt also has the same affect on the canal-bed. This is due to the eventual breakdown of the concrete by the road salt, especially if the concrete is of poor quality. When repair or replacement of these manhole/catch basin structures is required, due to a deteriorated canal-bed, base or cone, the procedure is extremely expensive, time consuming, and difficult. Hence, there is a further need for an inside drop capable of directing the fluid flowing from the expansion line into a particular desired portion of the canal bed and in a desired direction. The present invention meets these and other needs that will become apparent from a review of the description of the present invention.